This invention relates to arrangements and methods for the switching or routing of traffic in a communication network
Traditionally, two types of legacy telecommunication networks have been developed. The first type of legacy network is connection oriented and is used for the transport of narrow band voice traffic, typically carried in TDM frames. Such networks comprise for example synchronous or plesiochronous networks. The second type of legacy network is connectionless in nature and is used for the transport of broad band packet or cell-based data traffic. Such packet traffic includes for example Internet protocol (IP) traffic There is currently a drive towards unified networks which provide end to end transport for both voice and data services, and to this end the use of asynchronous transport has been introduced. This of course introduces the problem of supporting different protocols over a common network.
Asynchronous Transfer Mode (ATM) is the technology specified by the ITU-T as a broadband network technology suitable for all applications. For Internet protocol traffic however, ATM has proven to be less than fully effective at supporting Layer 3 routed applications, such as routed virtual private networks. This has led the IRTF (Internet Research Task Force) to specify multi-protocol label switching (MPLS) as a technology which inherits the desirable characteristics of ATM but is better matched to the Internet protocol. In particular MPLS provides a frame merge function in which data frames received from multiple sources are captured and sent out with a common label. This is key to support of Internet protocol Layer 3 Routed services. Service providers would ideally prefer a single network technology to support all of the services that they provide as this would achieve the lowest possible operational cost.
A particular problem with the introduction of a multi-service network is that of accommodating the various transport protocols and, in particular, that of providing end to end quality of service guarantees for high priority traffic such as voice. In particular, there is a need to provide a network that can carry both data and voice traffic at a local, national and international level while utilising a common transport protocol. A further problem with such a network is that of real time management of the virtual public/private networks that are established within the network. At present, each VPN manager requires a detailed knowledge of the network topology. In a large network this is a very significant operational tasks.
An object of the invention is to minimise or to overcome the above disadvantages.
In our co-pending application serial number 09/605,237 the use of a two-layer MPLS network in order to simplify the management of Virtual Public/Private Networks (VPN) is described.
According to a first aspect of the invention, there is provided a method of routing an information packet over a label switched path from an end station to a destination via an access network and a core network, the method comprising attaching to the packet a label stack identifying a quality of service capable connection from the end station via the access network to the core network and across the core network to the destination.
According to another aspect of the invention, there is provided a communications network arrangement comprising a multi-service core network comprising a plurality of nodes interconnected via quality of service capable tunnels and incorporating a frame-mode MPLS architecture, and an MPLS access network, wherein end-to-end QoS services are provided by defining a label stack which delivers packets through a sequence of tunnels in the core network defined by the stack.
Advantageously, the core network comprises a mesh of abstract nodes interconnected by tunnels and each comprising one or more real nodes.
In a further embodiment, the invention provides a method of routing an information packet over a label switched path between first and second end stations in a virtual private network defined over a network arrangement incorporating an MPLS layer and comprising a hierarchical arrangement of first, second and third levels of routers, the method comprising attaching to the information packet a four-label stack at the edge of the network in order to achieve end-to-end connection oriented behaviour with guaranteed Quality of Service, and wherein the label allocation of a said information packet is determined from the MPLS layer.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.